Rubber goods such as tire treads often are made from elastomeric compositions that contain one or more reinforcing materials such as, for example, particulate carbon black and silica; see, e.g., The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04.
Typically, filler(s), elastomeric material(s), and additives are chosen so as to provide a composition from which can be made rubber articles with an acceptable compromise or balance of performance properties such as traction, abrasion resistance, hysteresis, etc. Ensuring that reinforcing filler(s) are well dispersed throughout the elastomeric material(s) both enhances processability and acts to improve physical properties. Dispersion of fillers can be improved by increasing their interaction with the elastomer(s). Examples of efforts of this type include high temperature mixing in the presence of selectively reactive promoters, surface oxidation of compounding materials, surface grafting, and chemical modifications to the terminal ends of the polymers.
Where an elastomer is made by anionic polymerization techniques, attachment of certain functional groups is difficult due to the fact that carbanions, such as living polymers, are terminated by active hydrogen atoms such as are present in, e.g., primary and secondary amine groups. However, because amine functional groups provide desirable interaction with particulate fillers, particularly carbon black, commercially useful methods of providing living polymers with terminal amine functionality remain desirable. Because the interactivity with fillers tends to increase as the number of hydrogens bonded to the amino nitrogen increases, the provision of secondary and primary amine-functionalized polymers is particularly desirable.
One procedure for providing amine functionality to anionically initiated polymers is described by K. Ueda et al., “Synthesis of Polymers with Amino End Groups—3. Reactions of Anionic Living Polymers with α-Halo-ω-aminoalkanes with a Protected Amino Functionality,” Macromolecules, 1990, 23, 939-45. Anionic living polystyrene is reacted with an α-halo-ω-aminoalkane followed by de-protection of the trialkylsilyl-protected amine functionality to provide a primary amino-functionalized polystyrene. The utility of the described procedure is limited by the academic laboratory conditions employed, however. The impact of these limitations on the practical utility of the described procedure is recognized in other academic publications; see, e.g., R. Quirk et al., “Anionic Synthesis of ω-Dimethylamino-Functionalized Polymers by Functionalization of Polymeric Organolithiums with 3-Dimethylaminopropyl Chloride,” Polym. Int., 1999, 48, 99-108.
After a functionalized polymer has been blended with one or more particulate fillers, the resulting filled composition, commonly referred to as rubber stock, often must be stored for some time before being used to make articles therefrom. During the time intermediate creation and use, some characteristics of the rubber stock can be degraded under certain circumstances. Thus, developing methods for enhancing the useful longevity of rubber stock prior to use also is desirable.